MEDICAL PHYSIOLOGY

Detailed explanation-1: -Firstly, the glucose in the proximal tubule is co-transported with sodium ions into the proximal convoluted tubule walls via the SGLT2 cotransporter. Some (typically smaller) amino acids are also transported in this way.

Detailed explanation-2: -The solutes and water move from the PCT to the interstitium and then into peritubular capillaries. The reabsorption in the proximal tubule is isosmotic. The proximal tubules reabsorb about 65% of water, sodium, potassium and chloride, 100% of glucose, 100% amino acids, and 85-90% of bicarbonate.

Detailed explanation-3: -Sodium continues to be reabsorbed in this part of the tubule via sodium/proton exchangers and actively transported through the tubule wall to the bloodstream by the sodium/potassium ATPase.

Detailed explanation-4: -Most of the glucose entering the tubular system is reabsorbed along the nephron segments, primarily in the proximal tubule, such that urine is almost free of glucose. This is different in diabetes, where the filtered glucose exceeds the transport capacity of the tubular system for glucose and glucosuria occurs.